Common Symptoms

Gallbladder mucoceles are an inherited disorder of the liver affecting dogs. A mucocele is a gallbladder that is severely distended by mucus. It can result in inflammation (cholecystitis) and possible rupture of the gallbladder. Affected dogs usually present with vomiting, jaundice, loss of appetite and abdominal pain. If the gallbladder is not removed before rupture, the dog will become very painful and die. Though it is known that dogs inheriting one copy of the causal Mutation are at increased risk for this disease, the presentation of gallbladder mucoceles is variable between dogs and not all dogs inheriting a copy of the mutation will develop the disease. This suggests that there are environmental or other genetic factors responsible for modifying disease expression. Because gallbladder mucoceles have symptoms that are common to other diseases, it can be difficult to diagnosis without ultrasonography or surgery.

Testing Tips

Genetic testing of the ABCB4 gene will reliably determine whether a dog is a genetic Carrier of gallbladder mucoceles. Gallbladder mucoceles due to Mutation of the ABCB4 gene are inherited in an Autosomal Dominant manner with Incomplete Penetrance meaning that dogs only need to inherit one copy of the mutated gene to be at an increased risk of developing the disease. Each pup that is born to an affected dog has a 50% chance of inheriting one copy of the ABCB4 gene mutation and being at-risk for the disease. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood and because the mutation shows incomplete Penetrance, genetic testing should be performed before breeding. Until the exact modifying environmental or genetic factor is determined, genetic testing remains the only reliable way to detect disease associated with this mutation. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of dogs known to have the mutation is not recommended. Dogs that have not inherited the mutation have no increased risk of having affected pups. However, because there are other environmental and genetic factors associated with gallbladder mucoceles, a normal result in ABCB4 does not exclude gallbladder mucoceles in a pedigree.

There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.